ANTIACID PHARMACEUTICAL COMPOSITION IN THE FORM OF A SUSPENSION BASED ON SUCRALPHATE GEL

Abstract: Antiacid pharmaceutical compositions in the form of suspensions containing sucralphate gel as an active ingredient combined with suitable excipients and/or diluents.

Description: ANTIACID PHARMACEUTICAL COMPOSITION IN THE FORM OF A SUSPENSION BASED ON SUCRALPHATE GEL Field of the invention The present invention relates to antiacid pharmaceutical compositions in the form of suspensions containing sucralphate gel as an active ingredient combined with suitable excipients and/or diluents. State of the art Sucralphate, i.e. the complex of sulphated sucrose and aluminium hydroxide, is an antiulcer drug. It exerts an inhibitory action against pepsin and, as more recently found, a cytoprotective action. In the solid state, sucralphate reacts with the acids of the stomach giving a tacky mucosa-adhesive substance, denominated paste. Said tacky substance is deemed essential to secure the antiulcer activity of sucralphate: it adheres to the ulcers and maintains the pH of the gastric microenvironment at ideal values for pepsin activity inhibition. Due to sucralphate basicity, 1 g of product can neutralize approx. 13 mEq hydrogen ions. On addition to 0.1 N hydrochloric acid, sucralphate in powder form rapidly becomes tacky and adhesive, and yields approx. 10# of its antiacid power within 2 to 3 minutes. After said initial yield, even if the reaction medium is maintained under vigorous stirring, the reaction with the acid becomes very slow as it is hindered by the paste viscosity. Therefore, although sucralphate is suitable for the treatment of ulcers, it cannot be used as an antiacid. In fact, as well known to those skilled in the art, the therapeutic activity of an antiacid preparation depends not only on its absolute acidity neutralization, but also and especially on its acidity neutralization rate in the gastric environment. Advanced pharmacopoeias state that the therapeutic activity of an antiacid preparation is a function of two basic parameters: reaction rate and neutralization duration. The first parameter, i.e. the reaction rate, concerns acidity neutralization for a fast relief of the heartburn sensation (pyrosis) generally accompanying gastric hyperacidity; the second parameter, i.e. neutralization duration, concerns the development of a buffer action maintaining for an appropriate time the gastric lumen pH above the value at which said painful sensation is no more felt. As concerns the first parameter, sucralphate exerts a poor action: paste formation considerably slows down its reactivity and, therefore, a pH value compatible with pyrosis suppression cannot be obtained. As concerns the second parameter, sucralphate is unable to maintain the pH value reached for an appropriate time: theoretically it can maintain the gastric environment buffered, but in fact, against a continuous secretion of the gastric juice, it does not exert any buffering action due to the low reactivity of the paste that formed. It follows that sucralphate can exert an antiacid action only if chemically transformed into a specific antiacid product , as disclosed in EP 437406. Therefore , sucralphate powder cannot constitute an efficacious active ingredient of an antiacid preparation. EP 286978 by the Applicant discloses sucralphate in the form of gel , with particles dimensional distribution practically at the limit of colloidal size , which secures a very high specific surface of the product. Sucralphate gel exerts a more potent antiulcer action than the powder form of general use and, when contacted with acids, does not form the paste already mentioned. The higher activity of the product was proved to result from its specific ability to adhere to the mucosa, i.e. from the bioadhesion, taking place without any intervention of the acids. The sucralphate gel aqueous suspension shows unique thixotropic-type Theological properties revealing a considerable surface activity of the particles, which very easily gives rise to interactions both with one another and with the biological substrates. Brief description of the drawings Fig. 1 illustrates the change of pH on addition of 0.5N HC1 to 1 g of sucralphate gel and, respectively, sucralphate powder at 25°C. Fig. 2 shows the antiacid effectiveness by Rosset-Rice's test and the results obtained with antiacid doses as per Examples 1, 2, 3, Fig. shows the antiacid effectiveness by Rosset-Rice's test and the results obtained by testing doses of 1 g sucralphate powder, 1 g of sucralphate gel, and 2 g of sucralphate powder. Summary of the Invention It has surprisingly been found that sucralphate gel shows a rate of reaction with the acids and acidity neutralization power decidedly superior to sucralphate in the powder form, as elucidated in Fig. 1. This figure illustrates the change of pH on addition of 0.5N HC1 to 1 g of sucralphate gel and, respectively, sucralphate powder at 25°C. It is an object of the present invention to provide antiacid pharmaceutical compositions in the form of suspensions containing sucralphate gel as an active ingredient, combined with suitable excipients and/or diluents, particularly suitable for the treatment of pyrosis and gastroesophageal backflow. Detailed description of the invention According to US Pharmacopoeia USP XXII, an antiacid preparation is generally considered safe and effective when it obeys the safety and effectiveness requirements ("Antiacid Effectiveness" requirements). To meet said requirements, the product has to pass a preliminary test meant to establish whether it may be defined antiacid or not. Said test consists in causing a single minimum dose of substance supposed to be antiacid to react with 0.5N hydrochloric acid for 10 minutes. Should the substance being tested under such conditions be capable of bringing the solution pH to values above 3-5. the preparation will be considered antiacid. Should said preliminary test give positive results, a second test will be conducted to determine the acidity neutralization power of the substance. Said power must be such that the aforesaid single minimum dose of the substance supposed to be antiacid can neutralize at least 5 mEq of acid. It has surprisingly been found by the Applicant that sucralphate gel at 37°C shows an acidity neutralization rate allowing it to pass the USP XXII preliminary test. In particular, in the preliminary antiacid effectiveness test as per USP XXII, already a dose of 1.5 g brings pH to values exceeding 3-5. In the second antiacid test, which is meant to determine the neutralization power, the said dose was found to neutralize 23 mEq against the limit value of 20 to 25 mEq set by USP XXII. Vice versa, in the preliminary test, the same dose of product containing commercially available sucralphate powder gives pH values ranging from 1.2 to 1.6. Evidence is thus provided that sucralphate powder is unable to exert an antiacid action. The sucralphate gel content in the suspension preferably ranges from 10 to 20% w/v. In particular, the therapeutic compositions of the present invention contain 1.5 to 4 g sucralphate per dosage unit and, preferably, 2 g sucralphate per dosage unit. Furthermore in water dispersion sucralphate gel is self-suspending: in other words, no other suspending agent is needed to obtain stable suspensions. Therefore, sucralphate gel can be used as a suspending agent to prepare antiacid suspensions in which other antiacids are stably suspended. The use of sucralphate gel as a suspending agent allows obtaining a safe and effective sucralphate-based antiacid preparation matching two important goals. First, the antiacid action of sucralphate gel may be strengthened by the addition of a dose of another antiacid with the result that a more potent antiacid action is obtained. Second, the use of sucralphate in conjunction with another antiacid active ingredient, such as for example magnesium hydroxide or salts thereof, brings a therapeutic benefit: i.e. the astringent effect on the intestine function typical of sucralphate is limited by the laxative effect typical of magnesium salts. It follows that the claimed compositions may also contain another conventional antiacid, if any, said antiacid being preferably selected among magnesium hydroxide, magnesium carbonate and calcium carbonate. In this case, 1 g of sucralphate was found to be sufficient for an optimal antiacid-suspending effect. The preferred dose of sucralphate, when combined with another antiacid active ingredient, preferably ranges from 1 to 3 S and the dose of said antacid active ingredient ranges from 0.250 to 0.750 g. The following examples of antiacid preparations obtained according to the present invention are conveyed by way of indication, not of limitation. EXAMPLE 1 One 10 ml dose of suspension contains: Sucralphate gel (corresponding to 927 sag Al(OH)o) 1.500 g Methyl-p-hydroxybenzoate sodium salt 0.020 g Propyl-p-hydroxybenzoate sodium salt 0.010 g Sorbitol 70 2.700 g Apple flavouring 0.014 g Purified water q.s. p-Hydroxybenzoates were dispersed in liquid sorbitol and wet sucralphate gel was added. The resulting mixture was dispersed to give a thick and fluid cream, which was added with the flavouring agent, made up to volume with water, turbine-stirred without air embodiment, to yield a fluid and translucent suspension. EXAMPLE 2 One 15 ml dose of suspension contains: Sucralphate gel (corresponding to 1,324 mg Al(OH) ) 2.000 g Methyl-p-hydroxybenzoate sodium salt 0.030 g Propyl-p-hydroxybenzoate sodium salt 0.015 g Sorbitol 70 4.600 g Apple flavouring 0.014 g Purified water q.s. This suspension was prepared according to Example 1. EXAMPLE 3 One 7ό ml dose of suspension contains: Sucralphate gel (corresponding to 662 mg Al(OH)n) 1.000 g Magnesium hydroxide 0.281 g Methyl-p-hydroxybenzoate sodium salt 0.016 g Propyl-p-hydroxybenzoate sodium salt 0.008 g Sorbitol 70% 2.300 g Apple flavouring 0.014 g Purified water q.s. This suspension was prepared according to Example 1. EXAMPLE 4 One 7-5 ml dose of suspension contains: Sucralphate gel (corresponding to 662 mg Al(OH)o) 1.000 g Magnesium carbonate 0.400 g Methyl-p-hydroxybenzoate sodium salt 0.016 g Propyl-p-hydroxybenzoate sodium salt 0.080 g Sorbitol 70 2.300 g Apple flavouring 0.014 g Purified water q.s. This suspension was prepared according to Example 1. The test as per USP XXII conducted on the formulation of Example 1 for the determination of the antiacid effectiveness gave the following results: preliminary antiacid power (pH > 3-5): pH 3- neutralization power (>20.25 mEq): 23 mEq. The test as per USP XXII conducted on the formulation of Example 2 for the determination of the antiacid effectiveness gave the following results: preliminary antiacid power (pH > 3-5) : pH 3•85 neutralization power (>28.93 mEq): 27 mEq. The test as per USP XXII conducted on the formulation of Example 3 for the determination of the antiacid effectiveness gave the following results: preliminary antiacid power (pH > 3 - 5) '• pH 5-6 neutralization power (>21.73 mEq): 27.0 mEq. The test as per USP XXII conducted on the formulation of Example 4 for the determination of the antiacid effectiveness gave the following results: preliminary antiacid power (pH > 3-5): pH 5-6 neutralization power (>21.8 mEq): >28.3 mEq. ROSSET-RICE DYNAMIC TEST Rosset-Rice's dynamic test (N.E. Rosset and M.L. Rice, Gastroenterology, 26, 940, 1954) was also conducted on the preparations of the present invention further to prove the effectiveness of the antiacid dose of same. According to this test, a 400 ml beaker containing water (70 ml) and 0.1N HC1 (30 ml) maintained at 37°C was fed with a dose of antiacid. After addition of 2 ml/min of ION HC1 the change in pH was measured under continuous magnetic stirring (300 rpm/min) . The antiacid dose is considered effective when a pH value of 3-0 is reached within 10 minutes and maintained above said value for over one hour. With reference to the figures, the Rosset-Rice's test provided evidence that all products possessed antiacid effectiveness. Sucralphate gel at a dose of 1 g shows some antiacid power and sucralphate powder at a dose of 2 g reaches a pH value of 3 within 10 minutes, but cannot maintain said value for over 15 minutes, during which 2 ml/min HC1 was added to simulate gastric secretion.

Claims: CLAIMS 1. Antiacid pharmaceutical compositions in the form of suspensions containing sucralphate gel as an active ingredient combined with suitable excipients and/or diluents. 2. The pharmaceutical compositions according to claim 1 suitable for the treatment of pyrosis and gastroesophageal backflow. 3- The pharmaceutical compositions according to claim 1 wherein the sucralphate gel content in the suspension preferably ranges from 10 to 20% w/v. 4. The pharmaceutical compositions according to claim 1 wherein the amount of sucralphate per dosage unit ranges from 1.5 to 4 g. 5- The pharmaceutical compositions according to claim 4 wherein the amount of sucralphate per dosage unit is 2 g. 6. The pharmaceutical compositions according to claim 1 wherein another antiacid active ingredient of the conventional type, if any, is also present. 7- The pharmaceutical compositions according to claim 6 wherein the other antiacid agent is selected among magnesium hydroxide, magnesium carbonate and calcium carbonate. 8. The pharmaceutical compositions according to claim 6 wherein the dose of sucralphate gel ranges from 1 to 3 S and the dose of the other antiacid active ingredient ranges from 0.250 to 0.750 g per dosage unit.

Inventors: ZAGNOLI GIORGIO, ZAGNOLI, GIORGIO
Applicants: LISAPHARMA SPA, ZAGNOLI GIORGIO, LABORATORIO ITALIANO BIOCHIMICO FARMACEUTICO LISAP, ZAGNOLI, GIORGIO
Application year: 1994
Main classification: A61K31
IPC codes: A61K9, A61K31, A61K33